Method and arrangement for choosing a target with a definite order number by means of a target seeker



Aplll 21, 1970 L. w. SJOSTROM 3,508,258

METHOD AND ARRANGEMENT FOR CHOOSING A TARGET WITH A DEFINITE ORDER NUMBER BY MEANS OF A TARGET SEEKER Filed July24. 1968 2 Sheets-Sheet l I l I FIG. 2

INVENTOR. LARS WERNER 5-.155 TR5M A T'TORNEYS Apnl 21, 1970 L. w. SJOSTROM 3,508,258

METHOD AND ARRANGEMENT FOR CHOOSING A TARGET WITH A DEFINITE ORDER NUMBER BY MEANSOF A TARGET SEEKER Filed July 24. 1968 2 Sheets-Sheet 2 la .6 [b g FIG. 3

INVENTOR.

AARS WERNER $|J5$TR5M ATTORNEYS United States Patent US. Cl. 343-5 2 Claims ABSTRACT OF THE DISCLOSURE A target seeker in a high speed carrier such as a missile has associated therewith apparatus for choosing a target having a given ordinal number from a group of targets approaching the carrier. The ordinal numbers are assigned on the basis of the distance of the target from the carrier. The apparatus effectively counts the on-coming targets as they enter a definite distance range band and when the target having the given ordinal number enters the band, the apparatus emits a signal. The signal can be used to initiate hunting or arming devices.

This invention relates to target seekers in a high speed carrier LfOI selecting a particular target from a plurality of targets.

Within missiles or carriers there are target seekers which must select a particular target from a group of targets which are different distances from the seeker, for example, the second nearest target or the fifth nearest target, etc. In other words, it must ignore a given number of on-coming targets before selecting a target.

Briefly, the invention contemplates counting the targets as they pass through a given distance range band from the carrier and emitting a signal only after a given number of targets have passed through the distance range band.

The invention will hereinafter be described in greater detail with reference to the accompanying drawing, in which FIG. 1 shows an example of a situation picture of a rapidly moving carrier and a number of targets, FIG. 2 shows an embodiment of an arrangement according to the invention and FIG. 3 shows another embodiment of the invention.

In FIG. 1, which is a situation picture of the target seeker, such as a search radar, and the targets, reference B denotes the rapidly moving target seeker carrier, references M11, M12, M2, M31, denote the different oncoming targets, references 1, 2, 3 n denotes the first, the second, the third etc. target rows (ordering of the targets with respect to distance from the carrier), references a and b denote distance range circles, limiting a chosen distance range band within which a signal is to be released when the chosen numbered target enters the band, and z denotes the maximum range of the target seeker.

FIG. 2 shows an embodiment of an arrangement according to the invention. References S1, S2, Sn denote a number of interconnected stages, one for each possible target row choice, reference S1 corresponding to the nearest target row, reference S2 corresponding to the second nearest target row, etc. References 1, 2, 3, n denote wires which can be either activated or inactivated. Each wire is associated with a different ordinal numbered target. These wires constitute one inlet of each of the AND-circuit G1, G12 Gln which exists in each stage. The other inlet of each of these AND-circuits is in all the stages except stage S1 connected to the outlet of a second AND-circuit G22, G23

G212. Concerning the first stage S1, the other inlet of the AND-circuit G1 is connected directly to the inlet I of the arrangement. The AND-circuits G22, G23 G221 have two inlets each. The inlets are connected in parallel to the inlet of the stage, one of them directly and the other one via a delay circuit F2, F3 Fn. The delay of the circuits is chosen in such a way that it corresponds to the time needed for a target to pass through the previously mentioned distance range hand between the circles a and b in FIG. 1. The delay circuits are of the kind which delay only the first signal passing therethrough, while the succeeding signals pass through undelayed.

When the targets of target row No. 1 (FIG. 1) enter the distance range band ab, i.e., the nearest targets enter the band, a signal is obtained at the inlet I and the signal is supplied to one inlet of the AND-circuit G1. If the target 1 the closest target has been chosen as the selected target the wire No. 1 is activated 'While the other wires are inactivated. Thus, the other inlet of the AND-circuit G1 is activated and a signal is obtained at the common signal outlet U of the arrangement as an indication that the chosen target is within the distance range band ab. In other words, if the first oncoming target was selected as the desired target, when this first oncoming target enters the range band a signal is given. The input signal across the inlet I also goes to the two inlets of the AND-circuit G22, to one of them directly and to the other one via a delay circuit F2 where it is delayed by the time '1'. After this time the target has already passed through the distance range band ab and the signal on the first inlet has ceased, so that the AND-circuit G22 will not emit a signal. If, instead target 2, had been chosen, i.e., the second nearest target was the selected target, the signal re sulting from that target entering the distance range ab goes directly via AND-circuit G22 (delay circuit F2 no longer giving any delay) to one of the inlets of the AND- circuit G12. The other inlet of AND-circuit G12 is activated by signal on the current-carrying wire 2 so that an output signal is transmitted, via OR-circuit B, to the outlet U. The signal across the input terminal I also goes to the two inlets of the AND-circuit G23, to one inlet directly and to the other one across a delay circuit F3, where it is delayed by the time 7. However, the signal on the first inlet ends before the delayed signal passes through the circuit. When the targets of target row No. 3 passes the distance range band ab, current is immediately supplied to the inlet of the AND-circuit G13 connected to the outlet of G23, and if the targets of target row No. 3 had been chosen, i.e. if the wire No. 3 is activated, an output signal is obtained. If on the other hand for instance the targets of target row No. 4 has been chosen, no output signal is obtained. The arrangement operates in a corresponding manner until all the target rows have passed the distance range.

FIG. 3 shows another embodiment of an arrangement according to the invention. Like in the previous figure references S1, S2 Sn denote a number of interconnecting stages, one for each possible target row choice, S1 for the nearest target row, S2 for the succeeding target row etc. References 1, 2, 3, n denote wires, which can be either activated or inactivated. The AND-circuits G1, G12, G13 etc. in FIG. 2 correspond to the AND- circuits G1, G12, G13 etc. in FIG. 3. The AND-circuit in FIG. 2, one inlet of which goes via a delay circuit and the other inlet of which is connected to the inlet of this delay circuit is also shown in FIG. 3 but feeding the inlet thereof is a further AND-circuit G32, G33, G3. In relation to the stages in FIG. 2 each stage has a further inlet, connected to a further common inlet Ib, generating a signal if there is a target between the distance range band, limited by the circles a and b, and the distance or range limit of the target seeker. In each stage but the last the inlet Ib is connected to the inhibit inlet of AND- circuits G41, G42, G43, The second inlet of these circuits in the stages S2 to Sn-l, is connected to the outlets of AND-circuits G22 to G2(n-1), respectively. The second inlet of AND-circuit G41 of stage S1 is connected to inlet la. The outlets of AND-circuits G1 and G4 of stage S1 are connected to the inlets of OR-circuit B1 Whose outlet is connected to common OR-circuit B, similarly for stages S2 to S(n1). Like in the previous embodiment it is of interest to get an input signal when targets come into the distance range ab, but in this case it is also of interest to get an input signal depending on Whether there are targets in the range behind" the distance range ab seen from the carrier, comp. FIG. 1. The range band bz (FIG. 1) will below be called a discovering gate, while the range band ab is defined as a locking gate. Out of the two inlets Ia and Ib, the inlet Ia receives signals from the locking gate and the inlet Ib receives signals from the discovering gate.

As long as all targets are in the discovering gate bz, i.e. when no target has yet come into the locking gate, signals from Ib cannot pass through the AND-circuit G1 or G32, and no output signal is obtained. When the target row No. 1 comes into the locking gate, signals will come to both inlets Ia and lb (provided that there is at least one target left in the discovering gate). If the target row No. 1 has been chosen, and the wire No. 1 is thus activated, the signal will pass via the inlet Ia the OR-circuits B1 and B, to the outlet U. If target No. 1 has not been chosen, no output signal is obtained, as it cannot pass through the AND-circuit G1, and the delay circuit F2 prevents the signal from reaching the AND-circuit G22. The described process is repeated, when the succeeding target rows come into the locking gate, as long as at least one target is left in the discovering gate. When, however, the last target row comes into the locking gate, an input signal is obtained only to the inlet Ia, and this signal can now pass through the AND-circuit G1 to the signal outlet U depending on the fact that the inhibition of the inhibition circuit G41 ceases. Thus, if the order number of the chosen target row will be higher than for the last occurring target row, an output signal is obtained when the last occurring target row has come into the locking gate.

I claim:

1. Apparatus associated with a. target seeker in a rapidly moving carrier for choosing a target with a given ordinal number up to a given maximum ordinal number from a group of oncoming targets wherein each target has an ordinal number based on its distance from the carrier and for generating a signal when the chosen target enters a definite distance range ban-d from the carrier, said apparatus comprising a first common inlet adapted to receive a signal whenever any target enters said definite distance range band, a plurality of stages,

each of said stages being associated with an ordinal number, the first of said stages comprising a first AND- circuit having an outlet and first and second inlets, said first inlet being adapted to receive a signal associated with the first ordinal number, said second inlet being connected to said first common inlet, each of said other stages comprising a first AND-circuit having an outlet and first and second inlets, said first inlet of each of said first AND-circuits being adapted to receive a signal representing the ordinal number associated with the stage, each of said other stages further comprising a second AND-circuit having an outlet and first and second inlets, the outlet of each of said second AND-circuits being connected to the second inlet of the first AND-circuit of its stage, respectively, a plurality of delay circuits. each of said delay circuits being connected to the first inlet of each of said second AND-circuits, respectively, means for connecting the outlet of the second AND- circuit of each of said other stages, but the last thereof, to the first inlet of the second AND-circuit and the delay circuit of a different one of said other stages, respectively, whereby said other stages are connected in cascade, the delay of each of said delay circuits being related to the time required for a target to pass through said definite distance range band so that the second AND-circuit of a stage is blocked when a signal is received by said common inlet which is associated with the target having the ordinal number associated with the preceding stage, and common outlet means connected to the outlets of all of said first AND-circuits for emitting a signal wherever one of said first AND-circuits emits a signal.

2. The apparatus of claim 1 further comprising a second common inlet adapted to receive a signal whenever a target is in a discovery region beyond said definite distance range band and a given maximum range, each of said stages except the stage associated with the maximum ordinal number further comprising a third AND- circuit having an outlet, an inhibitory inlet and a second inlet, the outlets of all of said third AND-circuits being connected to said common outlet means, each of said inhibitory inlets being connected to said second common inlet, the second inlet of said third AND-circuit of said stage associated with the first ordinal number being connected to said first common inlet, the second inlet of each of said third AND-circuits of said other stages being connected to the outlet of the second AND-circuit of the stage, respectively, and each of said stages except the stage associated with the first ordinal number further comprising a fourth AND-circuit having an outlet and first and second inlets, the outlet of each of said fourth AND- circuits being connected to the delay circuit and the second inlet of the second AND-circuit of the associated stage, the first inlet of each of said fourth AND-circuits being connected to said second common inlet, and the second inlet of each of said fourth AND-circuits of said stages being connected to the outlet of the second AND- circuit of the stage associated with the next lower ordinal number, respectively, so that at least one of the stages emits a signal to said common outlet whenever a target enters the distance range band and there are no targets in the discovery region.

References Cited UNITED STATES PATENTS 3,242,487 3/1966 Hammach 343-l2 X 3,298,024 1/1967 Btihm 34312 3,343,157 9/1967 Carre et al. 34313 X RICHARD A. FARLEY, Primary Examiner Us. 01. X.R. 3434. 13 

